<html><head><title>Add a constraint</title><meta name="HandheldFriendly" content="True"></head><body>Add a constraint<br><br><b>alter</b> <b>table</b> [database.[owner].]table <b>add</b> {[<b>constraint</b> constraint] { <b>unique</b> | <b>primary</b> <b>key</b> } [<b>clustered</b> | <b>nonclustered</b>] ({column [<b>asc</b>|<b>desc</b>]} <a href="w109049.html">(repeatable)</a> ) [<a href="q307271.html">index tuning options</a>] [<b>on</b> segment] | <b>foreign</b> <b>key</b> (column <a href="w109049.html">(repeatable)</a> ) <b>references</b>  [[database.]owner.]table [(column <a href="w109049.html">(repeatable)</a> )] [<b>match</b> <b>full</b>] | <b>check</b> (search_condition)}</body></html>